The present invention relates to a hard alloy comprising one or more hard phases and a binary or multicomponent binder metal alloy.
Hard metals or hard alloys have been described by R. Keiffer and F. Benesovsky, in "Hartmetalle," (1965), pages 216 to 223. Hard metals containing a basic carbide of chromium carbide (Cr.sub.3 C.sub.2) and 12% or 15% nickel binder are discussed therein which exhibit good wear resistance and high corrosion resistance. However, such chromium carbide hard metals are relatively brittle, which must be taken into consideration where impact stresses are concerned. Also, with increasing nickel content, the corrosion resistance of Cr.sub.3 C.sub.2 hard metals decreases. Moreover, use of Cr.sub.3 C.sub.2 hard metals as high temperature working materials is precluded by its insufficient toughness and poor resistance to alternating temperature stresses. Experiments in which Cr.sub.3 C.sub.2 has been partially replaced by Mo.sub.2 C, WC, TiC or TaC and in which nickel has been replaced by cobalt, copper, iron or molybdenum have not resulted in significant property improvements.
Another way to produce corrosion resistant hard metals is to replace the cobalt in WC-Co or WC-TiC-Co alloys, by corrosion resistant binder alloys. For this purpose, alloys of nickel and chromium in a ratio of 80:20 or 70:30 have been used. In practice, 6 to 20%, preferably 8 to 10% of such a binder alloy can be used in the hard metal.
A platinum bound WC hard metal has also been produced. This hard metal is recommended for construction of reactors subject to heavy neutron radiation. See Kieffer et al., p. 221.
Disadvantages of prior art hard alloys include their relatively low strength and/or their high specific weight.